The compound of formula I has valuable antibiotic properties. The compound can be used in the control or prevention of infectious diseases in mammals, both humans and non-humans. In particular, it exhibits a broad spectrum of anti-microbial activity including multi-drug resistant pathogens. The compound can also be administered in combination with known substances of antibacterial activity and exhibits synergistic effects with some of them.
Typical combination partners are e.g. sulfonamides or other inhibitors of enzymes which are involved in folic acid biosynthesis such as, for example, pteridine derivatives.
A current method of preparing compound I is described in the U.S. Pat. No. 5,773,446. The drawback of this synthesis is the lengthy synthesis and consequently the low overall yield. Most of the intermediates are not crystalline, which renders this synthesis economically less attractive as an industrial process. In addition, some expensive reagents cannot be recovered.
This problem is further complicated by the use of halogenated solvents, e.g. methylene chloride. Halogenated solvents are expensive to handle and to dispose properly, thus leading to an added cost.
Therefore, there is a need for a process for preparing the compound of formula I with a higher overall yield and a reduced number of reaction product isolation steps. There is also a need for a process where all isolated intermediates are crystalline and do not require chromatography.